Well tool coupling member



July 4, 1967 J- H. CURRENT WELL TOOL COUPLING MEMBER Filed Aug. 31, 1964 (/0079; (u/v e02 INVENTOR.

Bi (W United States Patent 3,329,450 WELL TOOL COUPLING MEMBER James H. Current, Houston, Tex., assignor to Schlumberger. Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Aug. 31, 1964, Ser. No. 393,058 4 Claims. (Cl. 287-2) This invention relates to coupling members for bridge plugs used in packing-off well bores; and, more particularly, to a new and improved weakened connecting stud member for permanent-type bridge plugs which member is so arranged as not to hinder the advancement of a rotary drill bit cutting away the bridge plug.

In certain types of well operations, it is often necessary to temporarily isolate or bridge-over a well bore. In such instances, it is customary to lower a permanent-type bridge plug to the desired depth into the well bore and secure the plug in place with a setting tool which is then removed. Then, when the bridge plug is no longer needed, it is drilled out wtih a conventional drilling bit.

In general, such bridge plugs consist basically of a central body or mandrel carrying upper and lower sets of normally retracted casing-gripping slips slidably arranged on slip-expanding devices or expanders. The expanders, in turn, are slidably mounted on the mandrel at opposite ends of a normally relaxed, elastomeric packing element or sleeve. The upper slips and expanders are appropriately arranged to be shifted downwardly on the mandrel to displace the packing element outwardly as the slips move into anchoring engagement with the casing. Once it is set, a locking device permanently secures the slidable upper members to the mandrel to maintain the bridge plug in this position. The metal parts are customarily made of such easily drillable metals as magnesium and cast iron.

A typical setting tool has an outer sleeve operatively arranged to shift the upper slips and expander downwardly as a central member of the setting tool pulls upwardly on the mandrel. This central member of the setting tool is usually connected to the bridge plug mandrel by a suitably weakened shear stud. Thus, after the bridge plug is set, as the central member continues to pull upwardly on the mandrel, the stud subsequently fails at a predetermined force and frees the setting tool for removal from the well.

The conventional shear stud is typically a cylindrical metal member having threads at each end and a weakened or reduced intermediate section. One end of the stud is threadedly received in a blind axial bore in the upper end of the bridge plug mandrel and the other end is similarly connected to the lower end of the central member of the setting tool. Thus, it will be appreciated that after the stud has been broken, the lower portion of the stud remains fastened to the bridge plug mandrel.

One particular problem commonly experienced in drilling through such permanent-type bridge plugs is that as the drilling bit cuts away the mandrel, the lowermost fragmentary end of the broken-off stud is driven out of its threaded engagement and falls into the conical bottom of the blind axial bore. Then as the drilling bit continues to cut away the mandrel, the apical portion or spear point of a typical multi-cone drilling bit will again engage the fragmentary stud portion. The cone with the spear point will, however, now be unable to obtain the necessary purchase or frictional engagement therewith to cut away this fragmentary stud portion since the fragment will freely spin within the conical recess forming the bottom of the axial bore, This often retards drilling through the bridge plug; and it is not at all unusual to spend an hour or more in merely cutting away at the small remaining fragmentary stud portion. Thus, it will "ice be appreciated that valuable rig time is often needlessly wasted in drilling out such bridge plugs.

Accordingly, it is an object of the present invention to provide a new and improved shear stud so arranged that it will be rapidly cut away by a conventional multi-cone drilling bit without impeding its advancement.

The present invention is accomplished by skewing the terminal end surface of that portion of a shear stud member that is to be engaged within a blind axial bore in a member of a well tool.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in con junction with the accompanying drawings, in which:

FIG. 1 illustrates an isometric view of a typical embodiment of the shear stud of the present invention;

FIG. 2 is a view of the upper portion of a permanenttype bridge plug set in a cased well bore and including a shear stud of the prior art; and

FIG. 3 'is a view similar to FIG. 2 wherein the bridge plug includes a new and improved shear stud depicted in FIG. 1.

Turning now toFIG. 1, one embodiment is shown of a shear stud 10 constructed in accordance with the prin. ciples of the present invention. The shear stud 10 is an elongated cylindrical member having a reduced-diameter or necked central portion 11 which is sized to fail at a predetermined tensile force. Conventional screw threads 12, 13 are formed on the opposite sides of the necked portion 11 and extend toward each end of the shear stud 10. So that the stud 10 will be reversible, both ends of the stud are skewed, as at 14 and 15, with intersecting transverse slots 16-19 cut therein. These slots 16-19 preferably extend substantially along the axis of the stud 10 and are terminated before reaching the necked portion 11.

Turning now to FIG. 2, the upper portion of a bridge plug 20 is shown as it would appear after being set in a cased well 21 and the setting tool (not shown) removed. A conventional multi-cone drilling bit 22 has already cut away the uppermost portion of the bridge plug mandrel 23 leaving only a fragmentary portion 24 of the lower end of a typical shear stud of the prior art. As depicted in the figure, the downward thrust of the drilling bit 22 has pressed the stud portion 24 out of engagement with mandrel threads 25 and the fragmentary portion has fallen into the conical bottom 26 of the blind axial bore 27,

As previously described, as the drilling bit 22 progressively cuts away the mandrel 23, the converging apical end or spear point 28 of the drilling bit cone 29 again comes into contact with the fragmentary stud portion 24. This fragmentary portion 24, however, is no longer secured against rotation relative to the mandrel 23 and accordingly will spin freely within the conical well or recess 26 to retard the cone 29 from continuing to cut away the remainder of the mandrel 23.

Turning now to FIG. 3, a view similar to FIG. 2 is shown, but with the new and improved stud 10 of the present invention being employed. The remaining fragmentary portion 30 of stud 10 has been dislodged from threaded engagement with the mandrel 31 and has dropped into the conical bottom 32 of axial bore 33 therein. Because of its skewed end 14, however, the fragmentary portion 30 will come to rest in the tilted position illustrated in FIG. 3. Thus, it will be appreciated that the lowermost edge 34 of the skewed end 14 will generally lodge near or in the junction of the conical bottom 32 with the straight Walls of the axial bore 33 and the opposite edge 35 of the fragmentary portion 30 will rest on the wall of the bore 33 opposite thereto.

Because it is tilted in a position such as shown in FIG. 3, the downward thrust of the drilling bit (not shown) will generally drive the edge 34 of the fragmentary portion 30 into the softer metal of the mandrel 31 or at least wedge it tightly in place. Thus, it will be appreciated that with frag-inentary portion 30 oo-rotatively secured in this manner, the fragmentary portion cannot free wheel to retard the drilling bit from continuing to cut away the mandrel. Furthermore, the transverse slots 17 and 18 in the fragmentary portion 30 so weaken it that the downward thrust of the drilling bit soon breaks the portion 30 into separate pieces which are then rapidly ground up as the drilling bit continues cutting through the mandrel 31.

Thus, it will be appreciated that the present invention has provided a new and improved weakened shear stud that will not hinder the cutting action of a conventional cone drilling bit as it cuts away a permanently set bridge plug within a well bore.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim of the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What isclaimed is:

1. As a sub-combination for use with a well tool within a well bore and having a longitudinal bore therein, a tension breakable member comprising: a cylindrical body having an upper end portion with means thereon adapted to be dependently connected to a suspension member extending into a well bore, a reduced intermediate breakable portion and a lower end portion with means thereon adapted to be received in a bore and engaged therein with a well tool, said lower end portion having a skewed terminal end surface and said terminal end surface being slotted with the slots extending through the body and axially to a point between the reduced intermediate breakable portion and the skewed terminal end surface.

2. As a sub-combination for use with a well tool within a well bore and having an internally threaded longitudinal bore therein, a coupling member comprising: a cylindrical body having an upper end portion with means thereon adapted to be dependently connected to a suspension member extending into a well bore, a reduced diameterintermediate portion and a lower end portion having external threads therearound adapted to be received in the blind bore and threadedly engaged therein with the well tool, said lowerend portion having a skewed terminal end surface and a plurality of slots opening at said end surface and extending through said body longitudinally in an axial direction into said body from said terminal end surface and to a point between the reduced diameter intermediate portion and the skewed terminal end surface.

3. An easily drillable tension stud for use in releasably coupling well tool parts in a well bore, one of said parts being adapted for removal from the well bore by a drilling operation, comprising: an elongate cylindrical member having a first portion adapted for connecting to said one part and an intermediate portion of reduced diameter sized and adapted to fail when a predetermined tensile force is applied thereto, said member further having a terminal portion between said first portion and an end surface of said member, said terminal portion having a smaller diameter than said first portion and being slotted along the central axis of said member with the slots extending through the member and longitudinally from said end surface to a point between the portion of reduced diameter and said end surface, said end surface being formed in a plane which is transverse to and skewed relative to the said central axis, whereby drilling of said 7 member, after destroying said first portion, can separate said terminal portion into plural parts which will not impede the drilling operation.

4. A destructible tension stud for use in releasably connecting well tool parts to one another comprising: an elongate cylindrical member having a first threaded portion for coupling to one well tool part and a second threaded portion for coupling to another Well tool part, said member having a reduced diameter neck portion between said threaded portions adapted to fail when a predetermined tensile force is applied thereto, said member further having smooth terminal portions between the ends thereof and said threaded portions, at least one of said terminal portions having at least one slot therein extending along the axis of said member from a location ad jacent to one of said threaded portions to an end surface of said member, said end surface being formed in a plane which is angularly disposed relative to a transverse plane passing through and normal to the central axis of said member.

References Cited UNITED STATES PATENTS 2,035,055 3/1936 Dyer 15l22 2,576,438 11/1951 Beach 151-70 2,647,584 8/1953 Baker et al. 166-134 3,131,764 5/1964 Muse et a1. 166123 CARL W. TOMLIN, Primary Examiner.

A. V. KUNDRAT, Assistant Examiner. 

3. AN EASILY DRILLABLE TENSION STUD FOR USE IN RELEASABLY COUPLING WELL TOOL PARTS IN A WELL BORE, ONE OF SAID PARTS BEING ADAPTED FOR REMOVAL FROM THE WELL BORE BY A DRILLING OPERATION, COMPRISING: AN ELONGATE CYLINDRICAL MEMBER HAVING A FIRST PORTION ADAPTED FOR CONNECTING TO SAID ONE PART AND AN INTERMEDIATE PORTION OF REDUCED DIAMETER SIZED AND ADAPTED TO FAIL WHEN A PREDETERMINED TENSILE FORCE IS APPLIED THERETO, SAID MEMBER FURTHER HAVING A TERMINAL PORTION BETWEEN SAID FIRST PORTION AND AN END SURFACE OF SAID MEMBER, SAID TERMINAL PORTION HAVING A SMALLER DIAMETER THAN SAID FIRST PORTION AND BEING SLOTTED ALONG THE CENTRAL AXIS OF SAID MEMBER WITH THE SLOTS EXTENDING THROUGH THE MEMBER AND LONGITUDINALLY FROM SAID END SURFACE TO A POINT BETWEEN THE PORTION OF REDUCED DIAMETER AND SAID END SURFACE, SAID END SURFACE BEING FORMED IN A PLANE WHICH IS TRANSVERSE TO AND SKEWED RELATIVE TO THE SAID CENTRAL AXIS, WHEREBY DRILLING OF SAID MEMBER, AFTER DESTROYING SAID FIRST PORTION, CAN SEPARATE SAID TERMINAL PORTION INTO PLURAL PARTS WHICH WILL NOT IMPEDE THE DRILLING OPERATION. 